title: Root proximity and inclination of orthodontic mini-implants after placement: cone-beam computed tomography evaluation.
abstract: BACKGROUND
  Root contact by mini-implants should be avoided. Prolonged contact can damage the root and might cause external root resorption. To reduce the proximity of a mini-implant to the root, information about positioning of the implants and the variability of inclination is useful. The purpose of this study was to investigate root proximity and variability of the placement inclination of a mini-implant according to placement position.
  
  
  METHODS
  Fifty patients with 147 implants (diameter, 1.6 mm; length, 8 mm) were included. Cone-beam computed tomography images were taken of the area around the implant-placement site. The distances between the root and the mini-implant, and the vertical and horizontal inclinations of the placed implants, were measured.
  
  
  RESULTS
  Of 147 implants, approximately 20% were in contact with a root. The vertical inclinations of the mini-implants were 48.3° to 50.4° in the maxilla and 57.5° to 63.3° in the mandible. In the right maxilla, the incidence of root contact with the distal adjacent tooth was significantly greater than that with the mesial tooth.
  
  
  CONCLUSIONS
  One fifth of the mini-implants in this study contacted adjacent roots. During placement of mini-implants in the buccal maxillary right alveolar bone, contact with the root of the distal adjacent tooth should be avoided.
authors.affiliation: Department of Orthodontics, School of Dentistry, Nihon University, Tokyo, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Shinohara
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Motoyoshi
authors.forename: Yasuki
authors.initials: Y
authors.lastname: Uchida
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Shimizu
mesh_terms: D000293:Adolescent; D000328:Adult; D000539:Alveolar Process / Q000000981:diagnostic imaging; D019412:Anatomy, Cross-Sectional / Q000379:methods; D001641:Bicuspid / Q000000981:diagnostic imaging; D002508:Cephalometry / Q000379:methods; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D015921:Dental Implants; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging; D008437:Maxilla / Q000000981:diagnostic imaging; D008904:Miniaturization; D008963:Molar / Q000000981:diagnostic imaging; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D014092:Tooth Root / Q000000981:diagnostic imaging*; D055815:Young Adult
chemical_list: D015921:Dental Implants